You'll often see an "80 percent" metric used when discussing electric car charging at a fast charger.

There's a very good reason for this: While that first 80 percent may fly by in only a quarter to half hour, the last 20 percent takes one heck of a lot longer.

It's that last 20 percent that is now causing tensions between some electric car owners, and bringing up questions of etiquette when using a quick charger.

Do you hang around and hope to top up those final few percent before the next electric car owner wants to plug in? Or do you accept that charging past around 80 percent may see you there for another hour or two, and move on to let other owners top up?

The issue is that fast chargers are set to gradually slow down once that 80-or-so-percent mark has been reached, to prevent the battery from overheating.

This is fine if you only need to top up your battery, but causes an problem for those looking to squeeze every last kilowatt into their battery pack--particularly if there's a queue developing behind them.

Various solutions are suggested on the Facebook page, including setting fast chargers to stop at 80 percent to encourage users to move on quickly afterwards. Another user suggests a 15-minute cap--after 15 minutes, drivers can decide whether they really need another 15 minutes, or whether that's sufficient to get them to their next destination.

There are some good ideas rolling around, but ultimately it comes down to etiquette. Don't need those final few percent? Unplug and let someone else use the station...